The invention relates to a regulating apparatus for a fuel supply system for a mixture-compressing externally ignited internal combustion engine with a pressure-regulating valve, whose movable valve part is influenced from one direction by fuel pressure and a pressure spring and from the other by a temperature-dependent element which effects a temperature-dependent alteration of pressure. A regulating apparatus is already known in which the fuel-air mixture, when the internal combustion engine is started cold and until the motor's operating temperature is reached, is made leaner in a linear relationship by temperature-dependent means. This has the disadvantage that, immediately after the engine is started, very high proportions of noxious ingredients are found in the exhaust.